Monday, May 07, 2012

Anaerobic Digestion and How to Mix a Porridge Good Enough for Goldilocks and the Three Bears

We recently featured a posting in which Little Miss Muffet made an appearance in a discussion of on-farm AD, so we've been waiting for a chance to better that, no matter how tenuous the link! Hence, our title!

We are often told that the wet anaerobic digestion process, as used for the "standard" type mesophilic biogas digesters so commonly used on-farms and for food waste digestion, must be the consistency of a porridge. Like Goldilocks in the Three Bears nursery tale insisted, it must be just right. Not too hot, not too cold and no doubt also just the right consistency too.

Within an AD Plant the temperature is controlled by hot water heating pipes which are often fixed around the inner side of the perimeter wall, and use hot water from the jacket of the engine, otherwise known as (part of) the CHP output, and that is not hard to achieve. But, getting the consistency right and keeping it right while mixing the reactor completely for a good biogas yield is much trickier.

That's why we were interested to read the following press release from Landia, in the following application at the newly completed  Burdens’ AD plant. We hope that you find it of interest.

Landia’s Pumps Help Bring Healthy Gas Yields to Burdens’ AD Plant

Tough durable pumps from Landia are playing an integral part in the success of Burdens’ innovative anaerobic digestion biogas plant at Llangadog in Carmarthenshire, South Wales.

Designed with additional shredding knives to cut and pull raw waste into the pump at the AD plant’s reception tank, Landia’s 7.5kw MPTK-I Chopper Pump is proving extremely reliable and effective, according to Burdens’ Project Engineer, Arrash Shirani:

“With Landia we have developed a very efficient pre-treatment chopping and blending process.  We are achieving just the right consistency for the mixed feedstock, which results in very healthy gas yields”.

The hydrolysis tank at Llangadog is also served by a Landia pump that sends the blended material to the pasteurization unit.  This MPTK-I 2.2kW Transfer Pump offers high performance but with very low energy consumption.
“Importantly too,” added Shirani, “we have no downtime because both Landia pumps just keep on working, so we save on costs, time and hassle with maintenance, which is also a big benefit”.
Located on the edge of the Brecon Beacons by a Site of Special Interest (SSI), Burdens’ AD biogas plant at Llangadog operates in conjunction with a Carmarthenshire County Council civic amenity site – and also as a demonstration plant to test different types and combinations of feedstock.
The separated hydrolysis system from Burdens is a key part of this new type of plant for capacities of around 10-50 tonnes per week. By combining modular components that can be scaled up as demand increases, it helps manage the risk of large speculative investment. Every part of each sub- assembly is available off the shelf, and can be bolted together to develop increasingly larger systems, suitable for all possible AD requirements from 30 tonnes of waste per week up to 100 tonnes per week.

The process and monitoring systems enable maximum constant yields of biogas to be maintained, delivering increased efficiency – typically up to 30% better than existing methods – also with far less operator supervision required.

Landia, +44(0)1948 661 200,

Did we go too far with our Goldilocks and the Three Bears analogy? Did it get you to read this? You have the opportunity to comment! Why not give us your thoughts using the website commenting facility?

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